Gevent

===================


Features
--------

- Waiters on Event and Semaphore objects that call ``wait()`` or
``acquire()``, respectively, that find the Event already set, or the
Semaphore available, no longer "cut in line" and run before any
previously scheduled greenlets. They now run in the order in which
they arrived, just as waiters that had to block in those methods do.
See :issue:`1520`.
- Update tested PyPy version from 7.3.0 to 7.3.1 on Linux.
See :issue:`1569`.
- Make ``zope.interface``, ``zope.event`` and (by extension)
``setuptools`` required dependencies. The ``events`` install extra now
does nothing and will be removed in 2021.
See :issue:`1619`.
- Update bundled libuv from 1.36.0 to 1.38.0.
See :issue:`1621`.
- Update bundled c-ares from 1.16.0 to 1.16.1.

On macOS, stop trying to adjust c-ares headers to make them
universal.
See :issue:`1624`.


Bugfixes
--------

- Make gevent locks that are monkey-patched usually work across native
threads as well as across greenlets within a single thread. Locks that
are only used in a single thread do not take a performance hit. While
cross-thread locking is relatively expensive, and not a recommended
programming pattern, it can happen unwittingly, for example when
using the threadpool and ``logging``.

Before, cross-thread lock uses might succeed, or, if the lock was
contended, raise ``greenlet.error``. Now, in the contended case, if
the lock has been acquired by the main thread at least once, it should
correctly block in any thread, cooperating with the event loop of both
threads. In certain (hopefully rare) cases, it might be possible for
contended case to raise ``LoopExit`` when previously it would have
raised ``greenlet.error``; if these cases are a practical concern,
please open an issue.

Also, the underlying Semaphore always behaves in an atomic fashion (as
if the GIL was not released) when PURE_PYTHON is set. Previously, it
only correctly did so on PyPy.
See :issue:`1437`.
- Rename gevent's C accelerator extension modules using a prefix to
avoid clashing with other C extensions.
See :issue:`1480`.
- Using ``gevent.wait`` on an ``Event`` more than once, when that Event
is already set, could previously raise an AssertionError.

As part of this, exceptions raised in the main greenlet will now
include a more complete traceback from the failing greenlet.
See :issue:`1540`.
- Avoid closing the same Python libuv watcher IO object twice. Under
some circumstances (only seen on Windows), that could lead to program
crashes.
See :issue:`1587`.
- gevent can now be built using Cython 3.0a5 and newer. The PyPI
distribution uses this version.

The libev extension was incompatible with this. As part of this,
certain internal, undocumented names have been changed.

(Technically, gevent can be built with Cython 3.0a2 and above.
However, up through 3.0a4 compiling with Cython 3 results in
gevent's test for memory leaks failing. See `this Cython issue
<https://github.com/cython/cython/issues/3578>`_.)
See :issue:`1599`.
- Destroying a hub after joining it didn't necessarily clean up all
resources associated with the hub, especially if the hub had been
created in a secondary thread that was exiting. The hub and its parent
greenlet could be kept alive.

Now, destroying a hub drops the reference to the hub and ensures it
cannot be switched to again. (Though using a new blocking API call may
still create a new hub.)

Joining a hub also cleans up some (small) memory resources that might
have stuck around for longer before as well.
See :issue:`1601`.
- Fix some potential crashes under libuv when using
``gevent.signal_handler``. The crashes were seen running the test
suite and were non-deterministic.
See :issue:`1606`.


----

===================


Features
--------

- Update bundled c-ares to version 1.16.0. `Changes <https://c-ares.haxx.se/changelog.html>`_.
See :issue:`1588`.
- Update all the bundled ``config.guess`` and ``config.sub`` scripts.
See :issue:`1589`.
- Update bundled libuv from 1.34.0 to 1.36.0.
See :issue:`1597`.


Bugfixes
--------

- Use ``ares_getaddrinfo`` instead of a manual lookup.

This requires c-ares 1.16.0.

Note that this may change the results, in particular their order.

As part of this, certain parts of the c-ares extension were adapted to
use modern Cython idioms.

A few minor errors and discrepancies were fixed as well, such as
``gethostbyaddr('localhost')`` working on Python 3 and failing on
Python 2. The DNSpython resolver now raises the expected TypeError in
more cases instead of an AttributeError.
See :issue:`1012`.
- The c-ares and DNSPython resolvers now raise exceptions much more
consistently with the standard resolver. Types and errnos are
substantially more likely to match what the standard library produces.

Depending on the system and configuration, results may not match
exactly, at least with DNSPython. There are still some rare cases
where the system resolver can raise ``herror`` but DNSPython will
raise ``gaierror`` or vice versa. There doesn't seem to be a
deterministic way to account for this. On PyPy, ``getnameinfo`` can
produce results when CPython raises ``socket.error``, and gevent's
DNSPython resolver also raises ``socket.error``.

In addition, several other small discrepancies were addressed,
including handling of localhost and broadcast host names.

.. note:: This has been tested on Linux (CentOS and Ubuntu), macOS,
and Windows. It hasn't been tested on other platforms, so
results are unknown for them. The c-ares support, in
particular, is using some additional socket functions and
defines. Please let the maintainers know if this introduces
issues.

See :issue:`1459`.


----

====================


Features
--------

- Let CI (Travis and Appveyor) build and upload release wheels for
Windows, macOS and manylinux. As part of this, (a subset of) gevent's
tests can run if the standard library's ``test.support`` module has
been stripped.
See :issue:`1555`.
- Update tested PyPy version from 7.2.0 on Windows to 7.3.1.
See :issue:`1569`.


Bugfixes
--------

- Fix a spurious warning about watchers and resource leaks on libuv on
Windows. Reported by Stéphane Rainville.
See :issue:`1564`.
- Make monkey-patching properly remove ``select.epoll`` and
``select.kqueue``. Reported by Kirill Smelkov.
See :issue:`1570`.
- Make it possible to monkey-patch :mod:`contextvars` before Python 3.7
if a non-standard backport that uses the same name as the standard
library does is installed. Previously this would raise an error.
Reported by Simon Davy.
See :issue:`1572`.
- Fix destroying the libuv default loop and then using the default loop
again.
See :issue:`1580`.
- libuv loops that have watched children can now exit. Previously, the
SIGCHLD watcher kept the loop alive even if there were no longer any
watched children.
See :issue:`1581`.


Deprecations and Removals
-------------------------

- PyPy no longer uses the Python allocation functions for libuv and
libev allocations.
See :issue:`1569`.


Misc
----

- See :issue:`1367`.